Diisocyanates are a group of highly reactive, widely used low molecular weight chemicals, and are the most commonly reported cause of occupational asthma in developed countries. Yet, the mechanisms by which diisocyanate-induced asthma and those at risk. It has been theorized that reactive diisocyanates act as low-molecular weight haptens that trigger human T-cell responses. However, considerable uncertainty exists regarding the natural "carrier" proteins for diisocyanate in vivo and the putative T-cells central to eliciting asthma- related airway inflammation following exposure. We hypothesize that diisocyanates bind to specific proteins in human airways including, albumin and keratin-18, and that these diisocyanate asthmatics and exposed non-asthmatic workers manifest distinct T-cell responses to diisocyanate-conjugated protein antigens that will aid in understanding the pathogenesis of diisocyanate asthma and identifying these subjects. To test these hypotheses we will: (AIM 1) Further characterize biologically relevant diisocyanate-protein complexes that result following the exposure of normal human airway tissues and proteins, (AIM 2). Evaluate diisocyanate antigenicity at the T-cell based on in vitro responses t specific diisocyanate-protein conjugates, and (AIM 3) Determine the roles of different T cell subsets (i.e. CD4+, CD8+, alpha/beta, gamma/beta) in the pathogenetic immune response to diisocyanate-conjugated proteins, through in vitro studies with T cells derived from airway biopsies and peripheral blood of diisocyanate asthmatic and exposed control subjects. These studies build upon our previous work that has identified novel diisocyanate-protein conjugates that occur in vivo and has generated antigen-specific T-cell lines from human airway endobronchial biopsy samples. The experiments will utilize peripheral blood; bronchial lavage and airway biopsy samples from a well-defined population of diisocyanate asthmatic and control subjects enrolled in ongoing studies at the Yale School of Medicine. Together the results should provide significant insights into the pathogenesis of diisocyanate asthma.